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One of the negative features of Poland’s climate is the periodic occurrence of atmospheric droughts. The most frequent source of this phenomenon is the occurrence of long-term (sometimes lasting several weeks) rainless periods. The occurrence of these periods is connected with the persistence of a stationary east European high that joins with the Azores anticyclone via central Europe. In such situations, with the accompanying lack or insufficiency of atmospheric precipitation, a drought begins to develop gradually. First, a soil drought appears, followed by hydrologic drought. During a hydrologic drought, a decrease in the ground water flow into surface waters is observed, among other phenomena. This results in the reduction of water flow in rivers. During such periods, a significant drop in the level of underground waters, as well as drying of some springs and small water courses, is observed.
In its initial phase of development, a drought exerts its first negative effects on crops. Intensification of this phenomenon also causes disturbances in other sectors of the national economy. Droughts and their negative results do not pose the same threat to all areas of Poland, although in general the influence of droughts is stronger here than in the majority of central European countries. This situation is the result of a combination of natural and historic factors.
One of the areas of interest of the Institute of Meteorology and Water Management (IMGW) is continuous monitoring and assessment of the course of meteorological and hydrological phenomena occurring in all areas of Poland. When preparing an analysis of the course of successive periods of drought spells, specialists from the IMGW branch in Poznan noticed the absence of similar studies of this phenomenon in Polish literature. In an attempt to fill this gap, they catalogued all droughts that occurred in Poland from 1951 to 1990. The research methods adopted in this study, and also the general characteristics of droughts in Poland, are summarized in this article.